The present invention relates to an emergency key mechanism on a cylinder lock with a double locking cylinder and a locking coupling axially movably fitted therein. The mechanism comprises a coupling spindle and two coupling wings mounted in rotary manner thereon for the alternative coupling of a cam for the locking bolt arranged in rotary manner between the two locking cylinders in the center of the stator common thereto to one of the two cylinder rotors by alternative positive locking engagement of one of the two non-rotary coupling wings axially displaceable in the rotors in an opening of the cam web.
Emergency key mechanisms of this type are already known.
As is known, cylinder locks with double locking cylinders can exercise three different locking functions which will briefly be explained hereinafter.
With the simplest type of double locking cylinder, the door can at any time and without hindrance be opened or closed or locked or unlocked with the appropriate key from one or the other side. Thus, the private sphere, e.g., a hotel room or the inside of a dwelling is not protected.
As a further development of this locking function, a second locking function is obtained through incorporating a locking coupling between the rotors of the two locking cylinders. In this case, when a key is inserted or turned in the door from the inside, e.g., the inside of a dwelling, the door can no longer be opened from the opposite side, i.e., from the outside, so that the private sphere is protected.
However, these two locking functions, i.e., possible access from both sides at all times and the protection of the private sphere are not sufficient in old people's and convalescent homes, hospitals, clinics, old people's dwellings, hotels, etc. In such cases, it is necessary on the one hand to protect the private sphere, e.g., in an old people's home or hotel room, but on the other hand, it must be possible in an emergency, e.g., fire, flood, risk of death in the case of illness, etc. to open the locked door from the outside. It is intended that these two conditions should be fulfilled by the emergency key mechanism.
A disadvantage of the hitherto known emergency key mechanisms on a cylinder lock with double locking cylinders is that when changing the emergency status, e.g., on changing from an emergency function on one side to such a function on both sides, or for locking-technical reasons, the whole cylinder must be replaced so that prior planning is necessary which is, however, always linked with planning uncertainty. However, present day security consciousness and the dynamics of organization programs in factories and businesses require constant adaptation of the locking arrangements to the particular requirements even during the actual construction work, so that cylinders have to be modified and replaced and this always affects the emergency key mechanisms. It would therefore be advantageous if the emergency status of the cylinder could be achieved by merely replacing parts.
A further disadvantage of the known emergency locking mechanisms is that the emergency key could be made relatively easily from a normal key by filing away and the like.